Motor fuel



Apr. 29, 1924.

UNlTED STATES PAT THOMAS MIDGLEY, JR., OF DAYTON, OHIO ASSIG-NOR, BY MESNE ASSIGNMENTS, TO

OF DELAWARE.

MOTOR FUEL.

No Drawing.

To all whom it may concern Be it known that l, THOMAS MIDGLEY, Jr., a citizen of the United States of America, residing at Dayton. county of Montgomery, State of Ohio, have invented certain new and useful Improvements in Motor Fuel, of which the following is a full, clear, and exact description.

This invention relates to fuels and more particularly to a fuel for use in super-duty lnternal-combustion engines.

The principal object of the invention is to provide a fuel adapted for use in superduty internal-combustion engines, without the development of objectionable characteristics, and tending to greatly increase the efi'ective operation of the engine. Other ob jects and advantages of the present invendescription thereof.

tion will be apparent from the following As set forth in applicants copending plication, filed Oct. 4, 1918, Serial N2. 256,873, the erroneous conceptions heretofore prevailing that engine knock was caused by prematuring or preignition had made the development of an engine,.

of the four cycle or two cycle type, adapted to operate at high compressions, a seeming impossibility. The highest compressions heretofore attained in engines of this type have been in engines adapted for aviation Work, such engines being built to operate, at the earths surface, at compressions of substantially 125 pounds per square inch. And at these compressions, with the fuels heretofore available, it has been impossible to ru n the engines at the earths suface with an advanced spark since there is a knock.- ing of the engine when run even with a retarded spark, and a. highly deleterious knocking when run with an advanced s ark. Because of having to run the engine with a retarded spark it has not been practicable to attain high engine speeds at the earths surface and at low altitudes.

The desirability of having as high a compression as practicable whlle operating at the earths surface and at low altitudes is quite obvious, for as higher altitudes are attained, with corresponding decreases in the compressions within the cylinder resulting from the rarefied atmosphere existing at these higher altitudes, the power output of the engine will be considerably decreased.

Any increase in compression at the earths Application filed October 4, 1918. Serial No. 258,874.

surface therefore results not only in more efficient operation at lower altitudes but also in increased power output, and more efiicient operation, at higher altitudes. And the increase at higher altitudes due to higher compression is relatively greater than the increase at lower altitudes.

A fuel such as cyclohexane, which is described in my copending application above referred to, is capable of permittin the use of high compressions at lower altitudes without the development of the knock. Cyclohexane, however, is not capable of general use as a fuel because of its comparatively high freezing point. The freezing point of this fuel is approximately the same as that of water C.) and it is obvious, therefore, that it is not adapted for general aviation use inasmuch as airplanes frequently attain altitudes at which the temperature is Well below its freezing point. And the same thing would be true of the use of cyclohexane as a fuel at the earths surface. That is to say, it would not be a useful fuel when subjected to temperatures substantially below its freezing point.

The fuel forming the subject matter of this invention is one which has all the desirable characteristics of the fuel described in my copending application above referred to, namely; high heat value; high cr1 t1c al compression; clean burning characteristlcs (1ncluding non-polymerization); high. power output; small distillation range; low flash point; low end point; small viscosity variation and noncorroding characteristlcs. In addition the fuel of the present invention has a freezing point substantially below 0 C. and sufliciently low to permlt of its use under and conditions normally met with either in operation at the earths surface 01' in operation, as with airplane engines, at higher altitudes.

As set forth in my copendmg application fuels of the na hthene roup, such as cyclohexane, have t e clean urnin characteristies, the high heat value and t e high ent cal compression which make them capable of use in a super-duty engine at extremal high compressions say of 125 pounds an over without the development of the lm ock. I have found that if compounds of the character have added thereto substantial amounts of certain of the cyclic aromatic compounds the resulting mixture retains the desirable naphthene grou characteristics of the compounds of the and in addition has a freezing point su stantially below the freezing point of such naphthene. In the preparation of such a fuel heretofore I have preferably made useof a mixture of cyclohexane and benzene, but other mixtures may be used if desired, for example methyl cyclohexane, a member of the. naphthene group may be used as a substitute for cyclohexane, and toluene, one of the cyclic aromatic compounds, may be used as a substitute for benzene. Benzene, as is well known, is deficient in heat value as compared to gasoline, and also has the undesirable characteristic of liberating copious quantities of fluffy carbon deposit upon burning. In addition to these undesirable characteristics its freezing point is also high, being approximately the same as which has the desirable lar com ound.

the freeziniepoint of water. I have found that when nzene 18 mixed with cyclohexane within a certain range of proportions the resulting mixture displaysall of the desirable characteristics present in the cyclohexane, and that, in'addition, the mixture has a freezing point lower than the freezing point of either of its constituents. By varying the roportions of benzene and cyclohexane the reezing point of the mixture may be varied. So that there is produced a fuel mixture 0 clohexane, namely, a heat value substantlally higher than that of benzene, a high critical compression, is clean burning, and in addition, has a freezing point substantially below 0 C.

In adding benzene to cyclohexane increasing theproportion' of benzene decreases the freezing polnt until a certain definite proportion is reached after which further increasing the proportion of benzene raises the freezing point; In other words starting with 100% c' clohexane the freezing point, natu'rally, is the freezing point of this particu- If now benzene is added to the eye ohexane in increasing proportions the freezingjmint will continue to fall until the mixture comprises substantially 80% cyclohexane and 20% benzene, by volume.

7 When this proportion is reached the freezing point will be substantially -40 Fahrenheit or centi ade. Any further increase in benzene eyond this point causes the freezing point to rise until, where a fuel containing 100% benzene and no cyclohexane is reached, the freezing point will be thefreezing point of such benzene. In other words in combining benzene and cyclohexane there is a certain definite proportion which constitutes a eutectic of those two, variations in proportion from this neutectic' causing a rising of the freezing point of the mixture.

' It will thus be seen that the mixing of thecharacteristics of tions of the'two ingredients would have to be within the certain range of proportions. That is, if there were a great excess or too much of the benzene, its undesirable characteristics would still be presentv in the mixture. But over a substantial range of proportions of the two ingredients, the cyclohexane when mixed with the benzene results in a mixture whichhas all of the desirable characteristics present in cyclohexane and likewise has a freezing point lower than either of the constituents.

I prefer to use as a fuel, especially for the operation of airplane engines, this eutectic of cyclohexane and benzene, but it is quite obvious that where it is not necessary to use proportions of cyclohexane and benzene can be varied as desired in order to secure the cheapest fuel which issatisfactory under the conditions desired. And of course variations in the price of cyclohexane and benzene might readily make a eutectic quite desirable from the point of view of costs.

While I have described this improved fuel as being composed of cyclohexane and benzeneit is to be understood that I by no means limit myself to these specific constituents, inasmuch as other constituents of the naphtheme and aromatic groups might be coma fuel having such a low freezing point the mixture other than the 7 bined to produce a fuel having the same desira'ble characteristics, all coming within the scope of the appended claims. 1. A fuel for internal combustion engines of the character described; consisting of aeutectic mixture of cyclohexane and benzene.

2. A fuel for internal combustion engines of the character described; consisting of sub stantially 80% cyclohexane and 20% benzene.

3. A fuel for internal combustion engines of the character described, comprising a mixture of cyclohexane and benzene having a certain range of proportions such that the mixture preserves the cyclohexane characteristics of heat value substantially higher than that of benzene, high critical compression and clean burning, unaffected as such by the benzene, but at the same time such proportions lower the freezing point of the mixture beyond the freezing point of either constituent. I

In testimony whereof I affix my signature.-

THOMAS MIDGLEY, JR.

Witnesses J. W. WRIGHT,

Geo. ROBINSON. 

